Low-back pain is a major socio-economic concern in this country. Although the exact cause for low back pain is unclear, the degenerative changes of the intervertebral disc (IVD), a crucial component of the human spine, have been implicated as a possible primary etiologic factor. The long-term objectives of this project are: (1) to better understand the biomechanics of the IVD, (2) to delineate the biomechanical etiology of disc failure, (3) to elucidate the pathophysiology of low-back pain, and (4) to develop new, minimally invasive diagnostic tools for disc degeneration. The purpose of this pilot research is to develop new techniques and experimental protocols for the investigation of relations of material properties to tissue composition and structure. The specific aims are to (1) investigate effects of proteoglycan (PG) content and collagen matrix density on tissue hydration, (2) investigate electrical properties of normal and PG-extracted IVD tissues, and (3) investigate dynamic compressive behavior of normal and PG-extracted IVD tissues. Three experimental studies will be developed and performed in this project. They are: (1) measurements of water content and true density of solid matrix, (2) measurement of electrical conductivity, and (3) dynamic compression testing of normal and PG-extracted animal IVD tissues. The experimental data will also be analyzed using a mechano-electrochemical theory to elucidate the relations of material properties to tissue composition and structure. These studies will help to understand the mechanism for regulating tissue hydration, the effect of disc degeneration on material properties and biomechanical behavior, and the biomechanical etiology of disc failure in human IVDs. The results will be useful for the future development of theoretical modeling as well as minimally invasive diagnostic tools for disc degeneration.